Stretch films are widely used in a variety of bundling and packaging applications. For example, stretch films have become a common method of securing bulky loads such as boxes, merchandise, produce, equipment, parts, and other similar items on pallets. Such films are typically made from various polyethylene resins and may be single or multilayer products. An additive known as a cling agent is frequently used to ensure that adjacent layers of film will cling to each other.
An issue with conventional stretch films is that the edges of the film can be easily damaged, which may result in tearing or failure of the film during use. Typically, the edges of the film are prepared by transversely slitting individual roll widths of film from a wider width of film by means of a conventional sharp edge slitter assembly. Any defects that are introduced into the edges of the film during the slitting process can result in film failure during the application process. Dropping the film roll or any other abuse during handling may also create zones of weakness or tears in the edges of the film.
One method of reinforcing the edges of the film is to fold the edges of the material to form a hem. For example, U.S. Pat. No. 5,565,222 discloses an apparatus for hemming the edges of stretch film. The apparatus consists of a first hemming roller with a width less than the width of the film, guide bars located adjacent to the film's path of travel, and a second hemming roller. As another example, U.S. Pat. No. 5,531,393 discloses a film with folded edges. Folding occurs before the film is stretched and is achieved by means of folding fingers that project inwardly from the side plates of the apparatus.
As can be seen, edge folds make the film easier to use and reduce waste by making the film less susceptible to failure due to tears, rough handling, or excessive stretching. However, current methods provide for edge folding in a separate and secondary process after the film has been produced, which increases the time and costs of film production. Thus, there is a need for methods, systems, and devices which can efficiently fold the edges of the film in-process. There is also a need for methods, systems, and devices that can simultaneously fold each edge of multiple widths of film that have been cut from a wider width of film. Finally, there is also a need for methods, systems, and devices that can re-introduce a fold without operator intervention if the fold is lost due to defects in the film.